Oil-Based Lubricant Especially Useful for Precision Parts

ABSTRACT

A lubricant composition contains about 2 to 10 weight percent (wt. %) of tungsten disulfide; about 2 to 10 (wt. %) of a zinc dialkyl dithiophosphates (ZDDP); and an oil carrier.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C § 119(e) of U.S. Provisional Application No. 63/113,671 filed on 13 Nov. 2021, the entirety of the disclosure of which is incorporated herein by reference.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to lubricants and, more particularly, to lubricants that employ tungsten disulfide, and are particularly useful in situations that involve high pressure and the need to reduce wear.

BACKGROUND OF THE INVENTION

Lubricants have been used for centuries to reduce friction between moving parts. As many lubricants are derived from hydrophobic materials, lubricants have also been employed to keep moisture from contacting parts.

Some of the earliest lubricants that were used were derived from animal by-products, such as animal derived fats and oils. One of the animal oils used as a lubricant was whale oil. With the emergence of petroleum-based oils and vegetable-based oils, the use of animal-based oils as lubricants decreased. Because of hunting bans on whales, the use of whale oil as a lubricant has almost ceased entirely.

A wide variety of lubricants are in use today that serve an even wider variety of purposes. Some lubricants are very heavy and viscous lubricants, such as greases, which are typically made by using oil, such as mineral oil, and mixing it with thickeners such as lithium-based soaps. In contrast, oils are thin, lower viscosity liquids made of long polymer chains that often contain additives to impart desired extra properties. Oils come in a wide range of viscosities, and includes such things as motor oil, three-in-one oil, sewing machine oil, and bar and chain oil.

Another type of lubricant is a penetrating oil. Unlike lubrication oils and greases, penetrating oils are designed for infiltrating the tiny cracks between surfaces, to add lubrication, and to break up rust, as opposed to providing long-lasting lubrication. An example of such a penetrating oil is WD-40. A fourth type of lubricants are dry lubricants. Dry lubricants are made up of lubricating particles such as graphite, molybdenum disulfide, silicone, or PTFE (“Teflon”).

As alluded to above, the different lubricants have different properties, and as such, are designed for different purposes.

One purpose for which lubricants are used is for lubricating precision parts such as bicycle chains, motorcycle chains and the like. Lubricants for such precision parts are designed to achieve at least three primary purposes.

The first purposes to reduce the friction between the parts that are being lubricated with the lubricant. The second purpose is to reduce wear of the particular parts being lubricated. A third purpose of a lubricant is to prevent the part from rusting, by coating the part being lubricated to prevent water from interacting with the part and thereby causing rust.

Currently, there are two primary types of lubricants that are used with such precision parts. These two types include wet lubricants and dry lubricants.

Wet lubricants are applied to a chain as a liquid and remain as a liquid on your chain. The classic wet lubricant used on bicycle chains is three-in-one oil. Wet lubricants are currently produced that employ a wide variety of oil types, including petroleum-based oils, synthetic oils, mineral oils, and even sheep oil. Examples of currently available wet lubricants are shown in the chart below.

Lube name Lube type Green Oil Wet lube containing a plant extract that has similar properties to Teflon Muc-Off Wet Lube Wet lube Muc-Off Wet Weather Wet Lube Ceramic lube Weld Tite TF2 Synthetic oil-based Wet Lube Eco Sheep Every Day Sheep Sheep Oil based Lubricant WD-40 Bike-Lube Wet Lube Lucas Oil Chain Lube Penetrating Aerosol Wet Lubricant

Dry lubricants are often applied is a liquid, but are usually designed to dry out to leave the chain covered in the lubricating element, which usually comprises a waxy kind of deposit.

A dry lubricant often comprises a solid lubricating material such as PTFE (Teflon) that is contained in a volatile solvent. When the solid lubricant is placed in a volatile solvent, the resulting mixture is preferably thin enough to penetrate the cracks, crevices, and niches within a chain or other object that is being lubricated. Over time the volatile material evaporates, leaving behind the solid lubricant material, such as the Teflon to serve as a lubricant for the chain.

Dry lubricants have an advantage insofar as they are less “messy” than wet lubricants. Those who have worked on bicycles are probably familiar with the phenomena of changing a chain on a bicycle, and encountering a chain that is greasy that thereby causes the grease of the chain to get on one's hands and clothes.

This does not exist with dry lubricants as they are dry to the touch and typically are not as likely to stain hands and clothes. However, dry lubricants also have their drawbacks, as their performance characteristics are often inferior to the performance characteristics of wet lubricants.

One type of dry lubricants is wax-based lubricants. A typical wax-based lubricant uses the wax as a carrier and includes an additive such as Teflon, molybdenum disulfide, or tungsten disulfide. Wax lubricants operate by the wax being applied hot so that it can carry the additive to all parts of the item being lubricated, such as a bicycle chain. Over time, the wax cures and through use tends to melt away leaving the additive attached to all parts of the chain into which it is carried.

One benefit of wax-based lubricants is that the resulting lubricant additive, such as Teflon becomes burnished into the metal over time. Generally, well-designed wax lubricants perform better than either the liquid or other dry lubricants.

However, wax lubricants also have a drawback. In order to be perform properly, a wax-based lubricant should be applied to a very clean chain. If one were to apply a wax lubricant to an existing chain, one would need to remove the built-up grease, oil, and other materials on the chain such as by ultrasonically cleaning the chain.

Once cleaned, the wax-based lubricant can be applied to the chain and will perform well. However, the drawback is that many users do not wish to go through the additional step of cleaning the chain.

Examples of dry lubricants and waxed based lubricants are shown in the chart below.

Lube name Lube type Finish Line Teflon Dry lube containing Plus dry lube Teflon White Lightning Clean Ride Wax-based film Smoove Universal Chain Lube Wax based lubes Squirt Chain Lube Wax based lube Silca Super-Secret Chain Lube Hot wax-based lube

The various lubricants discussed above have a wide variety of performance characteristics along with a wide variety of costs. As a generally rule, the lubricants above do perform their function in a workman-like manner. Nonetheless, room for improvement exists.

In particular, room for improvement exists in providing a lubricant that has the potential to have the high-performance characteristics of a wax-type lubricant (or possibly better), with having the ease of application normally found with either wet or dry lubricants.

SUMMARY OF THE INVENTION

In accordance with the present invention, a lubricant is provided for lubricating precision components. The lubricant comprises an oil carrier comprised of a high-polarity ester oil. To this, a first quantity of zinc dialkyldithiophosphates (ZDDP) is added along with a first quantity of tungsten disulfide.

Preferably, the quantity of the high-polarity ester oil comprises between about 80% and 98% of the lubricant, with the first quantity of the ZDDP comprising between about 2% and 10%; and the first quantity of the tungsten disulfide apprising between about 2% and 10% of the lubricant. In a more preferred embodiment, the high-polarity ester oil comprises between about 90% and 95% of the lubricant by weight, and wherein the ZDDP and the tungsten disulfide comprise the remainder.

More preferably, the quantities of the ZDDP and tungsten disulfide are approximately equal. In a further preferred embodiment, the ZDDP and tungsten disulfide each comprise between about 2% and 5% of the lubricant by weight.

In a most preferred embodiment, the ZDDP and tungsten disulfide comprise between about 2.5% and 3.5% by weight of the lubricant.

The compositions disclosed herein are useful in reducing friction and reducing component wear during use.

Another advantage of the present invention is that it provides surprisingly friction free lubricant that employs a small enough quantity of expensive additives, such as the ZDDP and tungsten disulfide so as to make the lubricant not price prohibitive to consumers.

DETAILED DESCRIPTION

The present invention relates to a lubricant that is especially useful in lubricating precision parts. An example of a precision part with which the present invention is especially well-suited are bicycle components, and especially, bicycle chains and the gears and cogs with which they engage.

A bicycle chain comprises a series of links. Each of the links includes a plate, which intersects and pivots relative to a plate on an adjacent link. A pin extends transversely to the primary plane of the plate and provides the pivot point about which the two plates rotate with each other. As such, a chain is a somewhat complex machine that includes a large number of moving parts with the moving parts being the pivot points, which comprises the pins, and the plates which rotate about the pins.

Bicycle chains are prone to wear because of the nature of the stresses placed on the chains, and the movements of the respective parts of the chains. Stresses are placed on the chain both by the rotation of the plates around the pivot pins and the pull on the pivot pins when a force is exerted on the chain, especially when the user is peddling the bike hard when accelerating or climbing a hill.

Due to wear, it is suggested that a typical rider employing a typical chain and lubricant replace the chain at about every 2,000 miles. For a serious bicycle rider, who typically rides somewhere around 3,000 to 5,000 miles a year, this means that the rider will be required to replaces chain at least once or twice a year. The chain needs to be replaced since a worn chain is less efficient than a new chain. The inefficiency of a worn chain results in a greater watt loss and may cause additional wear to the components that the chain engages such as the gears on the crank sprocket and cassette.

As force is exerted on the chain, the chain tends to elongate which may cause a mismatch between the gears of the rear cassette and the front crank of the bike. This mismatch may result in a substantial potential expense to a rider to replace worn parts, since a rear cassette of a bike can cost close to $500, a front crank can cost $300 on a well-constructed bike, and a chain can cost $100.

In summary, the use of a good lubricant can have several benefits to the user. First, by reducing the friction between the components, the user can obtain more watts of power for a given exertion of energy, since less energy is being wasted in overcoming the friction between the chain and the components of the bike such as the gears of the cassette and crank.

A second benefit is that a good lubricant can reduce the wear on the chain and the components that it engages, thus enabling the user to increase the useful life of his chain and cassette and crank. This can save the user money by not requiring the replacement of these components as often as might be expected with a less robust lubricant.

From the standpoint of the cyclist and purchaser, the oil of the present invention gives several advantages over lubricants in the known prior art. In particular, the oil of the present invention is believed to provide a surprisingly good combination of efficiency in terms of energy lost while using the lubricant and durability in terms of wear.

In determining how to formulate an oil, the typical choice is between wear protection and efficiency. As used herein, the term “efficiency” generally refers to the difference between the energy delivered by the rider into the pedals and the energy transmitted to the wheels. Generally, using a lubricant with a lower viscosity results in an increase in efficiency. Such an oil is often referred to as “a fast oil”. Additives to the oil tend to increase viscosity. The increase in viscosity may help to improve the life span of the product by reducing wear and tear.

However, as with any higher viscosity oil, the additives tend to thicken the oil, and to therefore tend to make the oil a slower oil, i.e., make it less efficient. By analogy, running a high viscosity (relatively thicker) oil in your car will help to reduce wear and tear, but will also make it less efficient and thus reduce your gas mileage.

The lubricating compositions of disclosed herein surprisingly can achieve both an increase in efficiency and a decrease in wear of the lubricated parts. The oil is fast, but because the oil is believed to form a protective film over the chain, it helps to reduce wear and tear of the parts when compared to lubricants of the prior art. Surprisingly, the formula of the for the lubricants disclosed herein creates a “sweet spot” that achieves both desired characteristics of a chain lubricant, i.e., increased efficiency and greater protection against wear.

Testing has surprisingly shown that the lubricants disclosed herein generally have better wear characteristics than “slow oil, high-viscosity oils” containing additives that are designed for long wear. Surprisingly, the lubricants disclosed herein also provide better speed and efficiency characteristics than some of the lighter weight, low viscosity lubricants. These previously known lighter weight, low viscosity oils, while having high efficiency characteristics, have poor wear characteristics because they tend to evaporate or volatilize off the chain over time.

A common test that is used is to determine efficiency is to place a chain on a dynamometer and to measure the input effort placed on the chain in terms of watts. At the same time, the output of the chain is also measured in watts.

In a typical example, one will run the test by applying 250 watts of energy to the chain and then measuring the output. With a standard synthetic oil, such as Mobil 1® the difference between the input and the output watts may be in the range of about 10 to 12 watts.

Some of the best specialty bike chain wet-applied oils can achieve efficiencies as good as 4 watts loss. Similarly, some of the best specialty dry oils can at best achieve about 9 to 12 watts loss, which is significantly less efficient than some of the best wet-applied oils.

One commercially available wax-based oil, SILCA Super-Secret Chain Blend (Hot Wax), is a surprisingly efficient lubricant as it is able to achieve as low as a 3.5 watt loss.

Nonetheless, room for improvement exists with these lubricants. For example, the best wet oils provide great efficiency but have a problem with degradation. Over time the performance will drop significantly as the lubricant degrades.

As mentioned above, the dry oils do not have great efficiency and do not generally perform as well as the wet oils, but these dry oils do not suffer as much from the degradation issues of wet oils. Wax oils, while having desirable performance characteristics also have the drawback of being difficult to apply since the chain must be cleaned before it can be applied.

Another benefit sought for an oil, relates to the degradation of the oil, and the ability of the lubricant to resist degradation.

The lubricants disclosed herein comprise an oil carrier that includes two additives to improve lubricity and wear characteristics. The oil carrier preferably comprises a high-polarity ester oil. The two additives comprise zinc dialkyldithiophosphate (ZDDP) and tungsten disulfide. Preferably, the quantity of the high-polarity ester oil comprises between about 80% and 97% of the lubricant by weight, with the ZDDP comprising between about 2% and 10% by weight; and the tungsten disulfide comprising between about 1.5% and 10% of the lubricant by weight.

In a more preferred embodiment, the high-polarity ester oil comprises between about 90% and 96% of the lubricant by weight, and the ZDDP and the tungsten disulfide comprise the remainder. Also, the quantities of the ZDDP and tungsten disulfide are preferably approximately equal.

In a more preferred embodiment, the ZDDP and tungsten disulfide each comprise between about 2% and 5% of the lubricant by weight, with the remainder comprised substantially of the high polarity ester oil.

In a most preferred embodiment, the ZDDP and tungsten disulfide each comprise between about 2.5% and 3.5% of the lubricant by weight. In the embodiment that is likely to be sold by the applicant, each of the ZDDP and tungsten disulfide will preferably comprise about 3 percent by weight.

The lubricants disclosed herein may also include other chemical additives such as one or more anti-oxidants, including but not limited to diphenylamine.

As used herein the term “about” used with a value or a range of values generally means that the value or range of values may vary by plus or minus 20% of the stated value or range, or by plus or minus 10% of the stated value or range, or by plus or minus 5% of the stated value or range, or by plus or minus 2.5% of the stated value or range.

As stated above, the three primary chemical components of the lubricant are an oil carrier that preferably comprises a high-polarity ester oil; and two additives that comprise zinc dialkyldithiophosphate and tungsten disulfide.

HE Oil Carrier.

The oil carrier preferably comprises a highly polar ester oil type synthetic oil.

Typical synthetic oils are Polyalphaoletin (PAO) fluids. Polyalphaolefin (PAO) fluids are synthetic hydrocarbons designed to provide superior lubrication performance over a wider temperature operating range than petroleum oils and are typically less volatile. A first main advantage of PAO oils is low-temperature fluidity, which allows the oil to flow freer in extremely cold temperatures. Used in engine oils PAOs allow for an easier engine start with less cranking and more immediate protection.

Other advantages of PAOs include their generally low volatility (high boiling point) and high-temperature thermal stability. These features provide a greater resistance to evaporation and a greater level of resistance against breaking down in high temperatures. Use of PAOs in engine oils results in a greater cooling effect on engine components.

Ester oils are a variant of synthetic oils

Ester oils are polar. The polarity of ester oils, is believed to cause the ester molecules to be attracted to positively charged metal surfaces. As a result, the molecules line up on the metal surface creating a tough film with enhanced adhesion properties. That is believed to translate into a strong and persistent film providing superior lubricity, improved efficiency, and reduced wear. The polarity of ester oils also decrease their volatility. As a result, these oils may retain their viscosity and lubricity longer.

For these reasons ester oils have properties that make them a superior choice for use in connection with the present invention. One reason to use ester oil is its greater ability to bond with metals and to stick to the metals to which it bonds. PAOs, being non-polar are less attracted to metal surfaces resulting in less adherence to those surfaces

Two important properties to manage when creating a lubricant for the present invention are viscosity and ability to lubricate. Generally, there is a relationship between viscosity and molecular weight. From linear alkanes to polymers, bigger molecules are expected to be more viscous. However, this simple rule of thumb does not always apply to synthetic esters.

The viscosity is strongly dependent on the amount of branching, aromaticity, functionality and ease of rotation of the bonds that make up the molecule. As the structure becomes more branched, it is more difficult for the molecule to bend around and flow over itself.

Aromatic esters are usually more viscous because of the rigid aromatic ring. So, while it is true that molecular weight is related to viscosity, there are also ways to break this relationship when desired. This is particularly useful when the volatility profile requires a specific molecular weight and the application demands a certain viscosity.

Molecular weight is not the only factor that determines the viscosity of a synthetic ester, but it can certainly be used to increase viscosity when necessary. If the component acids and alcohols each have more than one reactive group, esters can be polymerized to any length.

The key property of a lubricant is that it is expected to lubricate. Lubricity is affected by how easily the molecule flows over itself and how well it competes for and coats the metal surface.

Esters are generally considered good boundary lubricants because they associate with metal surfaces and reduce the amount of metal-to-metal contact during sliding motion. Structural factors that impact lubricity include the chain length, the amount of branching and the location of linkages within the molecule.

Longer carbon chains, less branching and good polarity all favor boundary lubrication. Ester linkages are polar but can be less surface active if they are shielded by carbon chains.

Synthetic esters are designed from different acid and alcohol feed stocks, so the location of ester groups and type of carbon chains can be selected independently. The degree of polarity will largely be affected by the relative number of ester linkages, the positions of the ester linkages, the shielding of the ester linkages and the size and type of carbon chains used.

A variety of ester oil blends are currently available in arrange of viscosities and polarities. In the present invention, it has been found that the polar ester oil should have high polarity characteristics. Examples of ester oils meeting these criteria are commercially available from Chevron Specialty Chemicals, Fuchs Lubricants, Calumet Specialty Products Partners, among others.

Zinc Dialkyldithiophosphates (ZDDP)

The next component of the lubricant is zinc dialkyldithiophosphates, which are commonly known as ZDDPs, ZDDPs were first patented by Amsoil in the 1940s, and widely used in the 1970s. However, use ZDDPs has been largely abandoned in motor oils. ZDDP comprises a family of coordination compounds that feature zinc bound to the anion of a dialkyldithiophosphoric acid.

And exemplary structure of a monomeric zinc dialkyldithiophosphate is shown below:

They are soluble in nonpolar solvents, and the longer-chain R derivatives easily dissolve in mineral and synthetic oils used as lubricants. ZDDPs with alkyl esters of C₁ to C₁₄ come under CAS number 68649-42-3. In aftermarket oil additives, the percentage of ZDDP ranges approximately between 2 and 15%. Zinc dialkyl dithiophosphates have many names, including ZDDP, ZnDTP, and ZDP.

In addition to the ZDDPs represented by CAS number 68649-42-3, zinc dialkyl dithiophosphates useful in this invention include, but are not limited, to zinc dipropyl dithiophosphate, zinc dibutyl dithiophosphate, zinc dipentyl dithiophosphate, zinc dihexyl dithiophosphate, zinc diisopentyl dithiophosphate, zinc diethylhexyl dithiophosphate, zinc dioctyl dithiophosphate, zinc dinonyl dithiophosphate, zinc dodecyl dithiophosphate, zinc didodecyl dithiophosphate, and the like.

The main application of ZDDPs are as anti-wear additives in lubricants including greases, hydraulic oils, and motor oils. ZDDPs also act as corrosion inhibitors and antioxidants. They are almost ubiquitous in lubricants, and treatment rates are usually between 600 ppm for modern, energy-conserving low-viscosity oils to 2000 ppm of this additive in some racing oils.

Various mechanisms have been proposed for how ZDDP forms protective tribofilms on solid surfaces. In-situ atomic-force microscopy (AFM) experiments show that the growth of ZDDP tribofilms increases exponentially with both the applied pressure and temperature, consistent with a stress-promoted thermal activation reaction rate model. Subsequently, experiments with negligible solid-solid contact demonstrated that film formation rate depends on the applied shear stress.

The physical and chemical properties of any formulation vary somewhat depending on the specific alkyl groups present in the ZDDP. ZDDP additives are viscous liquids with molecular weights in the 400 to 2000 Dalton range. Their vapor pressures and fugacity are low.

ZDDPs are slightly-to-moderately soluble in water. Thermal stability, anti-wear protection, hydrolytic stability and cost performance vary depending on the type of ZDDP.

Aryl type ZDDPs provide excellent thermal stability but are less effective in terms of anti-wear protection and hydrolytic stability. The secondary alkyl type provides the best anti-wear protection and hydrolytic stability, but does not provide good thermal stability.

Tungsten Disulfide

Tungsten disulfide is an inorganic chemical compound composed of tungsten and sulfur with the formal chemical formula of WS₂. This compound is part of the group of materials called the transition metal dichalcogenides. It occurs naturally as the rare mineral tungstenite.

Tungsten disulfide is a low friction dry lubricant coating that improves performance and service life better than many dry lubricants by reducing friction and solving problems of excessive wear, seizing, galling, and fretting. Tungsten disulfide is inert, non-toxic, and non-corrosive, and can be applied to all stable metal substrates. It is impervious to most solvents, refined fuels, and chlorinated solvents. Tungsten disulfide is often employed because it achieves a dynamic coefficient of friction of 0.030 and static coefficient of friction of 0.070 to 0.090.

Currently, tungsten disulfide is used in a wide variety of applications, including lubrication of bearings, CV Joints, transmissions and differentials in automobiles, and various types of bearings such as ball bearings, taper bearings etc. that are used in a wide variety of applications. Another application in which tungsten disulfide is used is for lubrication of chains. Chains that are coated with tungsten disulfide are often able to run without wet lubrication, and benefit from lower friction.

Tungsten disulfide is commercially available from a wide variety of suppliers including Brycoat Inc of Oldsmar, Fla.; Ross Mill Co. of West Hartford, Conn.; Micro Surface Corp of Morris, Ill.; and ALB Materials of Henderson, Nev.

It has been discovered that it is preferable to use a tungsten disulfide material comprising a fullerene-type platelet. See Hazarika, S., & Mohanta, D. (2019). “Revealing mechanical, tribological, and surface-wettability features of nanoscale inorganic fullerene-type tungsten disulfide dispersed in a polymer.” Journal of Materials Research, 34(21), 3666-3677. doi:10.1557/jmr.2019.301 An example of a tungsten disulfide that will function in the present invention is a tungsten disulfide that is structured as a full ring that is about 200 to 600 nanometers in size.

Methods

The process for discovering the lubricant of the present invention was done by experimenting with different standard and newly created formulations. When a new formulation was created, the formulation was tested on a wear machine.

The wear testing procedure was employed to test for pin wear, wherein a 600 N load was placed on an American Society for Testing and Materials G77 (ASTM G77) test machine. To perform the test, lubricant is place on the pin, and a steel ring is rotated against the pin for a given period of time pursuant to the task, and then the amount of wear on the pin is measured. Typically, the wear would show itself by creating a flat on the generally cylindrical surface of the pin.

The amount of wear is generally proportional to the size of the flat. If the lubricant did not work well, one would get a rather large of wear area. Conversely, if the lubricant did work well, the area of the flat be smaller. If the lubricant worked very well, the result is a very small flat, or possibly just a pin-sized flat.

The loss of mass from the pin can be measured to get a more quantitative wear measurement factor.

In general, viscosities @ 100° C. and @ 40° C. are reported in cSt units and are measured according to ASTM D445. Viscosity @−40′C is reported in cSt units and is measured according to ASTM D2532. The unitless viscosity index is measured or calculated according to ASTM D2270.

Prior to the testing of new materials, the test was first run on a pin lubricated by Mobil synthetic oil manufactured by the Exxon Mobil Corporation. Mobil is a high grade PAO synthetic oil that has very good lubrication characteristics, and is used in automobiles. The Mobil was used as the base against which to compare other materials that were tested.

The first new material that was tested was an Ester Oil Blend bicycle chain lube branded as NFS, and sold by NixFrixShun at Nixfrixshun.com. The NFS is a type 5 ester-based oil. The NFS oil was found to be an improvement over the Mobil 1®. Prior to the discovery of the lubricants disclosed herein it was believed to be the state-of-the-art within the industry for chain lubricants.

Examples of Preferred Embodiments

An early attempt to develop an improved lubricant over the NFS lubricant was based on combining the ester-based oil with the tungsten disulfide as a lubricant additive. This combination proved to be about ten percent better than the NFS alone. It resulted in about 10% less pin wear when compared to original NFS.

Another attempt to improve the product was to combine an ester oil with ZDDP. The ester oil and ZDDP lubricant gave improved lubrication over the base NFS oil by about 15%. It was found that this ester oil-ZDDP combination performed better than the combination of the ester oil and the tungsten disulfide.

Another attempt to improve the lubricant involved using a 50-50 mixture of ZDDP and tungsten disulfide without an oil carrier. Surprisingly, the combination of a first material (tungsten disulfide) which resulted in a 10% improvement over NFS, with a second material (ZDDP) which resulted in a 15% improvement over NFS created a lubricant that through the combination of the two gave a 90% improvement.

Although these results were surprising and quite spectacular, room for improvement still existed. In particular, although the combination of ZDDP and tungsten disulfide had great performance characteristics, the combination also suffered from problematic economic characteristics.

In particular, both tungsten disulfide and ZDDP are very expensive. Currently, the price for ZDDPs is about $15.00 for 2 ounces. The price for tungsten disulfide is about $30.00 per ounce. As such, a 50-50 mixture of the two compounds, with no other additives, creates a surprisingly fantastic performing product, albeit one that would carry a price tag, that would likely make the product cost prohibitive to all but the most dedicated and affluent consumers.

To improve over the ZDDP-tungsten disulfide lubricant mixture, a product that would have similar performance characteristics, but would be less expensive to manufacture, and therefore, less expensive for the consumer to purchase was sought.

It might be expected that the dilution of the tungsten disulfide and ZDDP mixture by placing them in an ester oil carrier might reduce the performance of the resulting ester oil-ZDDP-tungsten disulfide mixture when compared to the ZDDP-tungsten disulfide mixture without the oil carrier.

When the ZDDP-tungsten disulfide mixture was placed in an ester oil, at about 2.5 percent by weight of each of the two components (that being 95% oil, 2.5% ZDDP and 2.5% tungsten disulfide) performance was degraded when compared to the 50 percent tungsten disulfide, 50 percent ZDDP mixture that contained no oil carrier.

Surprisingly, even when diluted, the ZDDP/tungsten disulfide in an ester oil carrier mixture performed better than the NFS base, and actually better than either of the tungsten disulfide-oil mixture and the ZDDP-oil mixture. As discussed above, the tungsten disulfide-oil mixture resulted in about a 15 percent improvement over just NFS, and the ZDDP-oil mixture gave about a 10 percent improvement over NFS.

The mixture of ZDDP and tungsten disulfide in ester oil showed a surprising synergism. When the two were combined at 2.5 percent ZDDP, 2.5 percent tungsten disulfide and 95% NFS type ester type oil, the ZDDP-tungsten disulfide-NFS oil mixture yielded an improvement of between about 60 and 85 percent ion wear reduction when compared to the baseline NFS. Viewed another way, this three-component combination yielded an improvement of somewhere between 50 and 75 less wear than the oil-tungsten disulfide or oil-ZDDP mixtures alone.

Examples of More Preferred Embodiments

Surprisingly, it was found that the mixture could be improved further by employing a high polarity ester oil, as opposed to the one used in the NFS oil. It was found that a solution comprised of 2.5 percent ZDDP, 2.5 percent tungsten disulfide, and 95 percent high polarity ester oil performed significantly and surprisingly better than any of the aforementioned combinations. Use of a polyol ester oil as the oil carrier for the lubricant is a preferred embodiment of the invention.

In an embodiment of the invention the lubricant comprises polyol ester oils having viscosities at 40° from about 5 cSt to 40 cSt, about 5 cSt to 30, or about 5 cSt to 25 cSt and having viscosity indices of about 110 to 200, or about 115 to 150, or about 115 to 140 as the oil carrier.

In an embodiment of the invention lubricants comprising ester oils resulting from the esterification of one or more polyols selected from the group consisting of neopentyl glycol, pentaerythritol, dipentaerythritol, trimethylolpropane, and the like, with one or more saturated fatty acids are preferred.

In an embodiment of the invention the lubricant further comprises up to about 3% of a calcium sulfonate oil additive. As used herein the term “calcium sulfonate oil additive” generally refers to a mixture comprising an alkyaryl sulfonate calcium salt. In an embodiment of the invention the calcium sulfonate additive used may be an overbased calcium sulfonate oil additive. A non-limiting example of an overbased calcium sulfonate oil additive is RB CS 425 (RB Products, Inc, Houston, Tex.). RB CS 425 has the following technical specifications.

Specific Gravity ASTM D 4052 1.08 (60° F.) Viscosity cSt ASTM D 445 82 (40° C.) Phosphorus, mass wt % ASTM D 4951 7.2 Zinc, mass wt % ASTM D 4951 7.85 Color, dilute ASTM D 6045 1.5 Sulfur, mass wt % ASTM D 4951 15

Testing showed that its wear resistance characteristics were 90% to 95% better than NFS. As will be appreciated, this is surprising because this solution, unlike other oil solutions, had performance characteristics that were not just close to the mixture of the oil-less ZDDP-tungsten disulfide mixture (90% performance improvement), but actually exceeded the performance of the oil-less ZDDP-tungsten disulfide mixture by five percent.

High polarity ester oils and high polarity polyol ester oils are available from Chevron Specialty Chemicals, Fuchs Lubricants, Calumet Specialty Products Partners and other specialty petroleum manufacturers and formulators known to those skilled in the art.

TABLE 1 Oil Carrier Additive Pin mass lost Mobil 1 100% PAO 10w40 none 0.22 gm Mobil 1 100% PAO 10w40 4% WS2 0.18 gm Mobil 1 100% PAO 10w40 4% WS2/4% ZDDP 0.05 gm Fuchs 100% Ester 10W40 none 0.17 gm Fuchs 100% Ester 10W40 4% WS2 0.13 gm Fuchs 100% Ester 10W40 4% ZDDP 0.11 gm Fuchs 100% Ester 10W40 4% WS2 + 4% ZDDP 0.01 gm

Several non-limiting embodiments of invention are disclosed in the following numbered clauses:

1. A lubricant composition comprising about 2 to 10 weight percent (wt. %) of tungsten disulfide; about 2 to 10 (wt. %) of a zinc dialkyl dithiophosphates (ZDDP); and an oil carrier.

2. The lubricant of clause 1 wherein the oil carrier is an ester oil.

3. The lubricant of any one of the preceding clauses wherein the synthetic ester oil is a polyol ester oil.

4. The lubricant of any one of the preceding clauses wherein the polyol ester oil has a viscosity at 40° C. of about 6 cSt to about 30 cSt.

5. The lubricant of any one of the preceding clauses wherein the polyol ester oil has a viscosity at 40° C. of about 8 cSt to about 25 cSt.

6. The lubricant of any one of the preceding clauses wherein the polyol ester oil has a viscosity index of about 110 to about 200.

7. The lubricant of any one of the preceding clauses wherein the polyol ester oil has a viscosity index of about 115 to 150.

8. The lubricant of any one of the preceding clauses wherein the polyol ester oil has a viscosity index of about 115 to 140.

9. The lubricant of any one of the preceding clauses wherein the wt % of tungsten disulfide is about 2% to about 5%.

10. The lubricant of any one of the preceding clauses wherein the wt % of ZDDP is about 2% to 5%

11. The lubricant of any one of the preceding clauses wherein the wt % of ZDDP is about 4%.

12. The lubricant of any one of the preceding clauses wherein the tungsten disulfide is a fullerene-shaped tungsten disulfide.

13. The lubricant of any one of the preceding clauses wherein the tungsten disulfide has a particle size of about 200 nm to about 600 nm,

14. The lubricant of any one of the preceding clauses wherein the wt % of tungsten disulfide is about 4%.

15. The lubricant of any one of the preceding clauses wherein about 25% of the tungsten disulfide has a particle size of 200 nm, about 25% of the tungsten disulfide has a particle size of about 400 nm, and about 50% of the tungsten disulfide has particle size of about 600 nm.

16. The lubricant of any one of the preceding clauses wherein oil carrier is a polyol ester resulting from the esterification of one or more polyols selected from the group consisting of neopentyl glycol, pentaerythritol, dipentaerythritol, trimethylolpropane, and the like, with one or more saturated fatty acids are preferred.

17. The lubricant of any one of the preceding clauses wherein the lubricant is a chain lubricant.

18. The lubricant of any one of the preceding clauses further comprising up to 3% of a calcium sulfonate oil additive.

19. The lubricant of any one of the preceding clauses comprising about 2% of a calcium sulfonate oil additive.

20. The lubricant of any one of the preceding clauses wherein the calcium sulfonate is an overbased calcium sulfonate oil additive.

21. A method of manufacturing the lubricant of any one of the preceding clauses, the method comprising: contacting the tungsten disulfide, ZDDP, and the oil carrier under conditions effective to disperse the tungsten disulfide and ZDDP in the oil carrier to manufacture the lubricant.

The above examples are merely provided for description of the present invention, and are not intended to limit the scope of the present invention. The objects of the present invention can be achieved by skilled persons in the art in accordance with the disclosure of the present invention and the parameter ranges involved. 

What is claimed is:
 1. A lubricant composition comprising about 2 to 10 weight percent (wt. %) of tungsten disulfide; about 2 to 10 (wt. %) of a zinc dialkyl dithiophosphates (ZDDP); and an oil carrier.
 2. The lubricant of claim 1 wherein the oil carrier is an ester oil.
 3. The lubricant of claim 2 wherein the synthetic ester oil is a polyol ester oil.
 4. The lubricant of claim 3 wherein the polyol ester oil has a viscosity at 40° C. of about 6 cSt to about 30 cSt.
 5. The lubricant of claim 4 wherein the polyol ester oil has a viscosity at 40° C. of about 8 cSt to about 25 cSt.
 6. The lubricant of claim 5 wherein the polyol ester oil has a viscosity index of about 110 to about
 200. 7. The lubricant of claim 6 wherein the polyol ester oil has a viscosity index of about 115 to
 150. 8. The lubricant of claim 7 wherein the polyol ester oil has a viscosity index of about 115 to
 140. 9. The lubricant of claim 8 wherein the wt % of tungsten disulfide is about 2% to about 5%.
 10. The lubricant of claim 9 wherein the wt % of ZDDP is about 2% to 5%
 11. The lubricant of claim 10 wherein the wt % of ZDDP is about 4%.
 12. The lubricant of claim 11 wherein the tungsten disulfide is a fullerene-shaped tungsten disulfide.
 13. The lubricant of claim 12 wherein the tungsten disulfide has a particle size of about 200 nm to about 600 nm.
 14. The lubricant of claim 13 wherein the wt % of tungsten disulfide is about 4%.
 15. The lubricant of claim 14 wherein about 25% of the tungsten disulfide has a particle size of 200 nm, about 25% of the tungsten disulfide has a particle size of about 400 nm, and about 50% of the tungsten disulfide has particle size of about 600 nm.
 16. The lubricant of claim 1 wherein the lubricant is a chain lubricant.
 17. The lubricant of claim 1 further comprising a up to 3% of a calcium sulfonate oil additive.
 18. The lubricant of claim 17 comprising about 2% of a calcium sulfonate oil additive.
 19. A method of manufacturing the lubricant of claim 1, the method comprising: contacting a tungsten disulfide, ZDDP, and an oil carrier under conditions effective to disperse the tungsten disulfide and ZDDP in the oil carrier to manufacture the lubricant. 